Lactate activated cement and activator compositions

ABSTRACT

Cementitious compositions in which the cementitious properties of fly ash are carefully controlled are described. The cementitious compositions may be substantially free harsh acids and bases such as citric acids (≈pH 2.2) and alkali metal activators including alkali hydroxides (≈pH 12-14) and metal carbonates (≈pH 11.6). The use of these harsh chemicals creates acid base reactions during use of the products. Instead of these harsh chemicals, a lactic acid salt based activator is be used as a reaction accelerator. Boric compounds may be used as a retarder in the compositions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Ser. No.13/004,303, filed Jan. 11, 2011, now U.S. Pat. No. 8,349,072, issuedJan. 8, 2013, which claims the benefit of U.S. Provisional ApplicationSer. No. 61/294,017, filed Jan. 11, 2010, the entire content of which isincorporated herein by reference.

FIELD OF THE INVENTION

A novel family of compositions is disclosed for the production ofblended hydraulic cementitious materials and their concrete and mortarderivatives for original construction, repair, manufactured concreteproducts, armor, spray and other applications. These materials exhibitcontrolled reactions of calcium-containing industrial byproducts withchemical activators, retarders, bond enhancers, and mechanical strengthmodifiers.

BACKGROUND OF THE INVENTION

Materials with pozzolanic properties contain vitreous silica and aluminathat will, in the presence of water and free lime, react with thecalcium to produce calcium silicate and calcium-alumina-silicatehydrates. There are both natural and industrial pozzolans.

Industrial pozzolans are produced during industrial processes andinclude, for example, Class C and Class F fly ashes as defined inaccordance with American Society of Tests and Materials (ASTM)specification C618. These fly ashes are produced during the combustionof coal. They consist of the inorganic, incombustible matter present inthe coal that has been fused during combustion into an amorphousstructure. The classification of industrial produced fly ash depends onthe type of coal used and its chemical composition. The combustion oflignite or subbituminous coal typically produces Class C fly ash. Thecombustion of anthracite and bituminous coal typically produces Class Ffly ash.

As defined by ASTM C618, the characteristics of Class C fly ash includehigher lime content than Class F fly ash. The higher lime content inClass C fly ash allows Class C fly ash to be self-hardening, while ClassF fly ash typically requires the addition of lime or cement to formhydrated cementitious materials.

An example of a natural pozzolan is Class N pozzolanic ash. Class Npozzolanic ash is a raw or calcined natural pozzolan such as somediatomaceous earths, opaline cherts, and shales; tuffs, volcanic ashes,and pumicites; and calcined clays and shales.

The chemical and physical attributes of Class C, Class F and Class Npozzolanic ashes are defined by ASTM-C618, the contents of which arehereby incorporated by reference in their entirety.

It is known to use fly ash in cement compositions, typically in thepresence of Portland cement. U.S. Pat. No. 5,556,458 to Brook, et al.,for example, requires at least 20% Portland cement. In particular,Brook, et al. notes that Portland cement is required in theircomposition to overcome the low early strength of fly ash compositions.

U.S. Pat. No. 4,997,484 to Gravitt et al. and U.S. Pat. No. 7,288,148 toHicks et al. disclose fly ash cement compositions without Portlandcement, but rely on an acid-base reaction system that utilize thecombined effects of citric acid (≈pH 2.2) and either an alkali hydroxide(≈pH 12-14) or metal carbonate (≈pH 11.6). However, the fly ash cementcompositions of Gravitt and Hicks do not exhibit the working time,strength, durability, and hardness required by many cement applications.

U.S. patent application Ser. No. 12/017,956, the entirety of which isincorporated herein by reference, describes improved cementitiouscompositions comprising pozzolan powders and a pH neutral activator, andin particular, a pH neutral citric salt.

BRIEF SUMMARY OF THE INVENTION

The present invention is based on the discovery that derivatives oflactic acid, lactate and the salts of lactic acid, when used as ahydration activator of pozzolanic cements, unexpectedly and surprisinglyimprove the cements' plastic properties such as slump retention andworkability. The improved slump retention and workability allows workersto conduct surface finishing operations to obtain desired textureswithout the time constraints associated with the use of citric saltactivators or activators employing the salts of other longer carboxylicacids. Interestingly, not all three-carbon carboxylic acids produce theadvantage of lactates. In particular, salts of proprionic acid, anotherthree-carbon carboxylic acid, were found not to produce the improvementsin retention and workability characterized by lactate activated cements.As described herein, a lactic acid, a lactate or the salt of lactic acidis used as the primary activator. As used herein, the phrase “chemicalactivator based on lactic acid” refers to lactic acid, a lactate, andsalts of lactic acid, activators.

According to some preferred embodiments, the activator is an alkalinemetal or alkaline earth salt of lactic acid. In addition, other forms ofneutralized lactic acid may be beneficial. According to other preferredembodiments, the activator is potassium, sodium, lithium, calcium ormagnesium lactate. In some embodiments, other activators may be presentin the cement compositions. Preferably, the lactate activator is presentin a weight percentage of at greater than 50% of the total activatorcontent of the cement composition, more preferably 95% of the totalactivator content of the cement composition. Stated alternatively,non-lactate activators should be present in a total amount of less than50% by weight, preferably less than 30% by weight, and more preferablyless than 25% by weight, of the total weight of all combined activatorsin the cement composition.

One embodiment is a cementitious composition including coal flyash-based pozzolans; and a chemical activator based on lactic acid. Thechemical activator may be a pH neutral salt of lactic acid. For example,the chemical activator may include potassium lactate, sodium lactate,lithium lactate, calcium lactate, or magnesium lactate. The pH neutralsalt may also include an alkaline metal or alkaline earth. In someembodiments, the cementitious composition may be substantially free ofcitric acid activators, alkali metal activators, and metal carbonateactivators.

In addition, the cementitious composition may further include a chemicalretarder. For example, the retarder may include a boron compound such asboric acid, boric oxide, sodium borate, sodium tetraborate, potassiumborate and potassium tetraborate, borax pentahydrate, and boraxdecahydrate. The cement may include a borate or other retarder, forexample, in an amount of 0.1 to 3.0 weight percent, based on the totalweight of hydratable cement.

The cementitious composition may have a set time of between 30 minutesand 12 hours, greater than 2 hours or even than 12 hours withoutdeleteriously affecting the ultimate performance properties, e.g.mechanical properties over a broad range of temperatures (40° F. to 120°F. Preferably, the cementitious composition has a set time of less than24 hours.

Another embodiment is a method of forming a hardened cement compositionincluding mixing a hydratable composition comprising coal fly ash-basedpozzolans and a chemical activator based on lactic acid to form ahardened cement composition. The method can further include mixing achemical retarder with the hydratable composition comprising coal flyash-based pozzolans and the chemical activator. In some embodiments, themethod could further include dissolving a retarder in a solutioncomprising the chemical activator in a concentration of between 0.1 wt %and 40 wt %, more preferably, between 0.1 wt % and 30.0 wt % and mostpreferably in a concentration between 10.0 wt % and 30.0 wt %. Accordingto another embodiment the retarders and/or other compounds may be in aseparate solution in other solvents at concentrations from 0.1 wt % to50 wt %.

Lactic salt or salts may be used in combination with other knownactivators or a single lactic salt or a combination of lactic salts maybe used as the sole activator. For example, potassium lactate may beused as the sole activator. Preferably, the non-lactate activators arepresent in a total amount of less than 40 wt %, and more preferably lessthan 25 wt %, of the total weight of all combined activators in thecementitious compositions. Boric compounds or other conventionalretarders may be used in the compositions.

The cement of the invention may include any source of pozzolanicmaterial whether naturally occurring or man made, including rice hullash, volcanic ash pumicites, opal and other shalls, diatomaceous earths,opaline cherts, tuffs, calcined clays, Class C fly ash, Class F fly ash,Class N pozzolanic ash, either alone or in combination. The cement mayalso include other additives, including silica fume, calcium aluminate,magnesium oxide, lime, gypsum, one or more retarding additives from theboron compound family (for example, borate salts, boric acid, boricoxide, or borax), organic retarders such as sodium gluco-heptonate,reactive clays such as meta-kaolin, wollastonite, air entraining agents(AEA), viscosity modifying agents (VMA), plasticizers, latex, fibers(for fracture toughness), or shrinkage compensation additives (SRA).Where the primary pozzolan powder is Class F fly ash or Class Npozzolanic ash, the cement includes one or more calcium-rich materials,preferably industrial byproducts such as cement kiln dust, lime kilndust, furnace slag and scrubber ash.

In some embodiments, the pozzolan powder may consist essentially of 100%Class C fly ash. In other embodiments, the hydratable cement mayalternatively include, for example, 50 to 95 weight percent Class C flyash based on the total weight of the hydratable cement; consistessentially of Class F fly ash and the cement may further include acalcium-rich material additive; include 0.5 to 50 weight percent Class Ffly ash based on the total weight of the hydratable cement; or consistessentially of Class N pozzolanic ash and the cement may furthercomprises a calcium-rich material additive. According to anotherembodiment, the pozzolan powder consists essentially of Class C fly ashand Class F fly ash, wherein the Class C fly ash is present in an amountof 50-100 weight percent, and the Class F fly ash is present in anamount of 0-30 weight percent based on the total weight of thehydratable cement.

The disclosed cements may be used alone or blended with other cementssuch as Portland cement, slag cements, and other types of conventionalhydraulic cements. However, the cements of the present invention do notrequire the presence of other cements in order to exhibit their superiorproperties. Accordingly, cements according to the invention may besubstantially free of Portland cement. The phrase “substantially free”means present in an amount of less than one weight percent based on thetotal weight of the referenced composition. The cementitiouscompositions may also include one or more fillers in addition to thecement. According to another embodiment, the hydratable cement may havePortland cement in amounts less than 20% by weight, and more preferablyless than 15%, less than 10%, and less than 2% by weight, based on thetotal weight of the hydratable cement. In some embodiments, the cementmay include sulfates or organic compounds.

In some embodiments, the cement compositions possess unexpectedly highdimensional stability, strength, hardness, working times, permeability,sulfate resistance, freeze-thaw resistance, mitigation ofalkali-aggregate reactivity, and/or easily controlled, wide range ofsetting times. According to another embodiment, a mortar, grout, orconcrete includes a hydraulic cement in which the cement is chemicallyactivated by a chemical activator based on lactic acid

Another embodiment is a hydratable cement that includes a pozzolanpowder, one or more pH neutral activators; and a retarder, wherein thehydratable cement has a calcium content expressed as the oxides of 15%or more, preferably 20% or more, based on the total weight of thehydratable cement, and wherein the pH neutral activators account forgreater that 50% of the total weight of activators in said hydratablecement and wherein the hydratable cement has less than 20% by weightPortland cement based on the total weight of the hydratable cement.

Yet another embodiment is a cementitious composition that includes ahydratable cement. The cement may include, for example, a pozzolanpowder; two or more activators, at least one of which is a lactic acidsalt; and a retarder; and one or more aggregate fillers. The aggregatefillers may include silica sand, natural sand, manufactured fineaggregate from stone production, bottom ash, slag, ground glass,recycled foundry sand, and recycled concrete and combinations thereof.

According to other embodiments, the hydratable cement may have alkalimetal and/or alkali earth metal activators in amounts of less than 30%by weight, and more preferably less than 25% by weight, of the totalweight of activators in said hydratable cement. According to otherembodiments, the hydratable cement may have alkali metal and/or alkaliearth metal activators in amounts less than 20% by weight, less than 15%by weight, less than 10% by weight, less than 5% by weight and less than2% by weight, based on the total weight of activators in said hydratablecement.

DETAILED DESCRIPTION OF THE INVENTION

Prior to the present invention, it was generally believed that hightemperature sintering (in the case of Portland cement) or a strongacid-base chemistry (in the case of prior art pozzolanic cements) wasnecessary to provide the strength and hardness required by most cementapplications. Subsequent to this prevailing view, the inventorsdiscovered that by using pH neutral activators, citric salts inparticular, cement products can be produced that have unexpectedlysuperior properties compared to Portland cement or to pozzolanic cementsprepared according to traditional acid-base activator chemistries.

Subsequent to the discovery of the advantages of citric salts asactivators, the inventors discovered that lactic acid, lactates, andsalts of lactic acid, when used as a hydration activator of pozzolancements, surprisingly improve the cements' plastic properties such asslump retention and workability. As used herein, the phrase “chemicalactivator based on lactic acid” refers to lactic acid, lactate, andsalts of lactic acid, activators.

The improved slump retention and workability allows workers to conductsurface finishing operations to obtain desired textures without the timeconstraints associated with the use of citric salt activators oractivators employing the salts of other longer carboxylic acids.Interestingly, it was also found that not all three-carbon carboxylicacids produce the advantage of lactates. In particular, salts ofproprionic acid, another three-carbon carboxylic acid, were found not toproduce the improvements in retention and workability characterized bylactate activated cements.

Described are cementitious compositions in which chemical activatorsbased on lactic acid are used as hydration activators to produceimproved plastic properties such as slump retention and workability. Theactivators dissolve or dissociate in the presence of water and pozzolansto allow the hydration reaction with the pozzolans to proceed in auniform, well controlled manner. Boric compounds, or other conventionalretarders, may be used in the compositions to slow or modify thehydration reaction. Where citric salt activators allow for set times inranges from as little as 10 minutes to 2 hours or more, lactic acid saltbased activators of the present invention allow for set times in therange of 30 minutes to 12 hours or more without significant loss inplastic properties. One skilled in the art would understand that thecompositions may be designed to have any number of desired set timesincluding between 30 minutes and 12 hours, greater than 2 hours, greaterthan 4 hour and greater than 6 hours.

Embodiments of this invention may also include combinations ofpozzolanic materials, for example, both Class C and Class F fly ash. Thereaction of Class C fly ash can produce considerable heat, and this heatcan cause early-stage shrinkage as the product is placed. This shrinkagecan result in cracking and delamination from a substrate. Class F flyash contains little or no calcium oxide (CaO), and is slowly reactivewith the lactate activator. Accordingly, the inclusion of some Class Ffly ash in the reaction mixture moderates the reaction forming the solidproduct by uniformly distributing strong, uniformly sized glassmicrospheres throughout the mixture. Additionally these thermalreactions are regulated by the use of the lactates. The method by whichthis is accomplished is by controlling the early conversion rate to thehydrated compounds. Consequently, while the total heat generated is thesame, the time to achieve the hydration is broadened which allows heatdissipation to the environment in a more controlled manner.

As with cements activated with citric salts, the cement materialsactivated with chemical activators based on lactic acid, upon reactionwith water, preferably include hydrates having silica to calcia molarratios (S:C) of from about 1:1 to about 1.8:1, typically from about1.1:1 to about 1.5:1. As particular examples, the S:C molar ratio may beabout 1.2:1, 1.3:1 or 1.4:1. The relative amounts of calcium-containingindustrial by-products (e.g., Class C fly ash) and low-calcium orsiliceous industrial by-products (e.g., Class F fly ash) may be selectedin order to achieve the desired S:C molar ratio.

Materials

The cements according to the present invention may include the materialsset forth below, in amounts expressed in terms of weight percentage ofthe entire cement composition, not including sand, stone and otherfillers. The term “cement” is generally used herein to refer to thebinder composition. The term “cementitious composition” is generallyused herein to refer to the combination of the cement (or binder) andfiller, for example sand, stone, and the like. The cementitious compoundtypically includes from about 5 to about 60 percent cement.

1) Natural or industrial pozzolan powders. Examples of pozzolan powdersinclude Class C fly ash, Class F fly ash, and Class N pozzolanic ash.The cementitious compounds may include Class C fly ash as a highcalcium-containing pozzolan powder. In some embodiments, Class C fly ashmay be included in the cement in the range of about 50 to about 98weight percent, within the range of about 60 to about 95 weight percent,or within the range of about 70 to about 95 weight percent. Preferably,the calcium content expressed as the oxides (CaO) of the high calciumcontaining pozzolan powder is higher than about 22 weight percent and isin the range of about 22 to about 30 weight percent. If the CaO contentis low, additional lime bearing components such as calcium hydroxide,nitrates, nitrites, sulfates or carbonates may be added. Note thatalthough the use of Class C fly ash as the high calcium-containingpozzolan powder is primarily described herein, other types ofcalcium-containing pozzolan powders may be used in some embodiments aspartial or total substitutes for the Class C fly ash (for example, blastfurnace slag, cement kiln dust, and lime kiln dust).

The cement may additionally or alternatively include one or morerelatively low calcium or high silicon containing pozzolan powders.Preferably, the cement includes at least one pozzolan powder with acalcium content expressed as the oxides of less than about 22 weightpercent or, more preferably, less than about 15 weight percent. In someembodiments, Class F fly ash may, for example, be present in the rangeof about 0.5 to about 50 weight percent, or preferably within the rangeof about 1 to about 25 weight percent, or more preferably within therange of about 2 to about 15 weight percent. Although the use of Class Ffly ash as the low-calcium pozzolan powder is primarily describedherein, other types of relatively low calcium and/or high siliconpozzolan powders may be used in some embodiments as partial or totalsubstitutes for the Class F fly ash (for example, Class N pozzolanicash, volcanic ash, bottom ash, wood ash, municipal incinerator ash,zeolites etc.) To the extent that low calcium content pozzolanic powderscomprise a large proportion of the pozzolanic powder component,calcium-rich materials must be added to the composition to provide therequired calcium content. Preferred calcium-rich materials includeindustrial byproducts such as blast furnace slag, cement kiln dust, limekiln dust and scrubber ash.

Silica fume may be used in the cement to increase short term strength,long term strength, bond strength, elastic properties and/or thermalproperties. When present, silica fume may be present, for example, inthe range of about 0.5 to about 10 weight percent, or preferably withinthe range of about 1 to about 7 weight percent.

Preferably, the cement comprises a total calcium content expressed asthe oxides of 20 weight percent or more. If the CaO content is low,additional lime bearing components such as calcium hydroxide, nitrate,nitrite, sulfate or carbonate may be added to achieve this calciumcontent.

Calcium aluminate may be used to increase the short-term strengthdevelopment of the product. Calcium aluminate may, for example, bepresent in the range of about 1 to about 25 weight percent, or withinthe range of about 5 to about 20 weight percent.

Lime (CaO or CaOH) additions can be used to enhance product workability,act as a shrinkage compensator, and/or function as an accelerator Limemay, for example, be present in the range of about 0.1 to about 5 weightpercent. The amount of lime added to the composition may be dependentupon the amount of lime present in the fly ash.

Borates may be used as strength gain retarders. Preferred boratesinclude one or more retarding additives from the borate salt family, forexample, borax may be present in the range of about 0.1 to about 10weight percent, or preferably 0.1 to 3 weight percent, or morepreferably from 0.1 to about 2 weight percent. Boric acid may also oralternatively be used as the borate may, for example, be present in therange of about 0.1 to about 10 weight percent, or preferably within therange of about 0.1 to 5 weight percent or more preferably within therange of about 0.2 to about 1.7 weight percent. Other borates such asboric acid, potassium borate, sodium borate, potassium tetraborate andsodium tetraborate hydrates may additionally or alternatively be used.These borates may be added to increase bond strength to the existingsubstrate as and is a retarder. Other known retarders including sulfatesand organic compounds can be used in addition or as an alternative tothe borates.

A single or multiple activators from the lactic acid family may beincluded. For example, lactic acid, lactate, potassium lactate, lithiumlactate, sodium lactate, calcium lactate or magnesium lactate may, forexample, be present in the range of about 0.1 to about 30 weightpercent, compared to the total weight of the cement, or preferably fromabout 2 to about 5 weight percent, compared to the total weight of thecement. These activators may be the only activators present in thecement. Alternatively, other non-lactate activators may be present,provided that lactate activators make up 50% or more of the activatorcomponent.

Other examples of pH neutral activators that may be used in place of orin addition to a lactate activator include citric salts, malic, malonic,glycolic, and other carboxylic acids and salts of these acids, includingbut not limited to nitrates, nitrites, chlorides, thiocyanates.

Miscellaneous ingredients including, for example, reactive clays such asmeta-kaolin, wollastonite, air entraining agents (AEA), latex, fibers(for fracture toughness), shrinkage compensators (SRA), viscositymodifying agent (VMA) and plasticizers.

In some embodiments, the cements of the present invention aresubstantially free of Portland cement, slag cements, and other types ofconventional cements. In other embodiments, the cements of the inventionmay include other cements, including Portland cement, provided that suchother cements comprise less than about 20 weight percent, preferablyless than about 15 weight percent, and more preferably less than 10weight percent, of the total weight of the cement.

Embodiments may also or alternatively be substantially free of alkalimetal activators such as alkali hydroxides (≈pH 12-14) and metalcarbonates (≈pH 11.6) as used in other types of materials. Embodimentsmay also or alternatively be substantially free of citric acids (≈pH2.2) and or other acids.

Cementitious compositions according to the invention may include one ormore fillers in addition to the cement. According to some embodiments,the fine aggregate (sand) particle sizes can range from fine silica sandto naturally or manufactured sand to conform to ASTM specifications.These fillers may include, for example, silica sand, natural sand,manufactured fine aggregate from stone production, bottom ash, slag,ground glass, recycled concrete and/or recycled foundry sands. Specificexamples of fillers include different aggregate gradations, such as C33sand, NJ 60 sand, C144 sand, #8 stone, and #57 stone or others.

This invention will be better understood with reference to the followingexamples, which are intended to illustrate specific embodiments withinthe overall scope of the invention.

EXAMPLES

Tables 1a and 1b provide examples of cement mixtures using a lactateactivator. Table 1a lists mixtures made at 95° F. and utilizing alactate activator at 72° F. Table 1b lists mixtures made at 72° F. InTables 1a and 1b the proportions of materials used in the mortarcompositions are; cement 6.91 lb (including activator), C33 Sand 10.80lb, water 1.59 lb. These proportions are mixed for 4 minutes and thenthe samples were prepared. The mortars tested had following approximatecomposition:

Class C fly ash ˜27.11 wt %

Class F fly ash ˜4.13 wt %

Retarder 0.4 wt % to 1.25 wt %

Activator 3.2 wt % to 10.0 wt %

C33 sand 66.7 wt %

Total 100.00 wt %

The total of the class c plus the class f fly ash is adjusted to accountfor differences in the amount of activator/retarder.

In these tables, the weight percentages for different activator andretarder compositions are provided. The lactate activator is comprisedof a 60 wt % solids solution of neutralized lactic acid. The salt is apotassium based salt. The retarder is a single source of technical gradeboric acid available from Rio Tinto Corporation.

The ability of these lactate mixtures to retain slump can be seen inTables 1a and 1b. The percentage of activator and retarder are basedupon the percentage of class C fly ash in the mixture. In Tables 1a and1b, the effects of the lactate to the retention of working time inmortars and concrete as determined in accordance with ASTM C 403 areshown. The flow retention time was greater than 2 hours (working time),and was measured by measuring the slump retention and placement time foreach composition. The final set time was from 2 hours to over 9 hoursand was measure by penetration resistance according to ASTM C403. Thestrength of the cement mixtures in psi are provided at 6 hours, 8 hours,24 hours, 7 days, and 28 days.

Variations to both the activator (potassium lactate) and of the retarderwere evaluated at different temperatures to determine what effect, ifany, to the slump or flow retention would occur. From this, it ispossible to formulate the cement to achieve desired properties.

TABLE 1a Cement Mixtures Made at 95° F.-Lactate Activator at 72° F. FlowFinal Retention set time, 6 8 24 7 28 Mix ID Description of mix Time,Min Min Hours Hours Hours Days Days 1 Lactate activator 5.8% liquid 217480 0 0 4387 6863 8775 (4.35% solid), Retarder1.25%. Lab made Lactateactivator 2 Lactate activator 5.8% liquid Flash Flash No samples made(4.35% solid), No Retarder set Set acid (0%) Lab made Lactate activator3 Lactate activator 6.33% 205 380 0 1041 4545 5982 8676 liquid (3.8%solid), Retarder1.12%. 4 Lactate activator 6.33% 150 270 0 1917 43887167 8787 liquid (3.8% solid), Retarder1.00%. 5 Lactate activator 6.33%100 131 0 2448 4207 6503 7859 liquid (3.8% solid), Retarder0.8%. 6Lactate activator 6.33% 28 35 2121 2462 3319 5922 liquid (3.8% solid),Retarder0.6%. 7 Lactate activator 6.33% 6 12 2354 2629 3774 6006 liquid(3.8% solid), Retarder0.4%. 8 Lactate activator 3.33% 230 600 0 0 44937253 8981 liquid (2% solid), Retarder1.0% 9 Lactate activator 5% liquid220 373 0 966 4567 7748 8238 (3% solid), Retarder1.0% 10 Lactateactivator 6.33% 150 270 0 1917 4388 7167 8787 liquid (3.8% solid),Retarder1.00%. 11 Lactate activator 8.33% 120 133 2035 2676 4296 6576liquid (5% solid), Retarder1.0% 12 Lactate activator 10% liquid 70 912240 2871 3948 5995 (6% solid), Retarder1.0%

TABLE 1b Cement Mixtures Made at 72° F.-Lactate Activator at 72° F. FlowFinal Retention set time, 6 8 24 7 28 Mix ID Description of mix Time,Min Min Hours Hours Hours Days Days 13 Lactate activator 3.33% liquid360 >540 0 0 1913 7833 8783 (2% solid), Retarder1.0% 14 Lactateactivator 5% liquid 300 498 0 0 3353 6184 8667 (3% solid), Retarder1.0%15 Lactate activator 6.33% liquid 240 352 0 723 3681 6877 9182 (3.8%solid), Retarder1.00%. 16 Lactate activator 8.33% liquid 180 225 547 9193541 6605 (5.0% solid), Retarder1.00%. 17 Lactate activator 10% liquid70 130 858 1315 3493 5863 (6.0% solid), Retarder1.00%. Variation ofRetarder 18 Lactate activator 6.33% liquid 240 352 0 723 3681 6877 9182(3.8% solid), Retarder1.00%. 19 Lactate activator 6.33% liquid 160 176845 1680 3498 6519 (3.8% solid), Retarder0.8%. 20 Lactate activator6.33% liquid 38 48 1630 1939 3363 5750 (3.8% solid), Retarder0.6%. 21Lactate activator 6.33% liquid 8 16 1618 1876 2944 5098 (3.8% solid),Retarder0.4%.

Various concrete mixtures made with a lactate activator can be found inTable 2. It can be seen that the workability of the concrete ismaintained without loss of slump up to the setting time. These concreteswere produced at different temperatures and targeted different workingtimes.

TABLE 2 Concrete mixtures made with lactate activators Example # 1 2 3 45 6 7 8 Pozzolan A (%) 17.482 15.783 15.783 15.783 15.783 15.783 15.78315.783 Pozzolan B (%) 2.995 2.704 2.704 2.704 2.704 2.704 2.704 2.704Retarder (%) 0.140 0.139 0.153 0.167 0.181 0.139 0.144 0.149 Lactate (%)1.108 1.131 1.131 1.131 1.131 1.131 1.131 1.131 SRA (%) 0.153 0.1150.115 0.115 0.115 0.000 0.115 0.115 C 33 Sand (%) 25.397 30.224 30.22430.224 30.224 30.224 30.224 30.224 # 57 Stone (%) 50.614 50.892 50.89250.892 50.892 50.892 50.892 50.892 Percent water 4.666 3.364 3.363 3.5423.362 3.602 3.370 3.370 Mix temp 50 70 70 70 70 70 70 70 Slump 4 4 3.756 4 6 4 3 Place time 4:24 8:09 9:00 Work time 2:01 5:02 8:30 3:15 2:453:14 Set time 1:00 missed 2:30 5:56 >9:08  >9:19  3:56 3:01 4:29Comments bleed bleed bleed water water water Strength 4 hours 395 5hours 330 450 6 hours 824 550 460 510 370 7 hours 580 610 430 8 hours575 485 10 hours 580 24 hours 1790 1800 1550 1180 1360 1800 1640 1490 48hours 3280 2970 2610 3060 3150 3160 2960 3 days 2870 3940 3780 3740 39105 days 4850 4620 4910 7 days 3660 5190 5180 4970 5180 5280 5020 5000 28days 6240 6090 6350 6600 6330 6250 6260

Table 3 shows the performance of a cement design with respect to variousconcrete designs. In these examples the cement formulation is asfollows;

Pozzolan A (Class C fly ash) wt % 82.08

Pozzolan B (Class F fly ash) wt % 13.90

Retarder (Boric Acid) wt % 0.903,

Activator (Potassium Lactate 60% solids) wt % 3.119

TABLE 3 Strength and Durability Results for Lactate Based Concrete MixCategory General Use Concrete Mix # 1 2 3 Binder Content/cy 600 lbs/cy750 lbs/cy 900 lbs/cy Strength 24 H 1120 2222 2424  7 D 3374 5453 589928 D 4831 6798 7310 Flex Strength 24 H 188 244 291  7 D 450 563 562 28 D553 647 685 Split Tensile 24 H 181 307 371  7 D 439 481 625 28 D 658 669660 MOE, Million 24 H 2.42 2.92 2.58 psi  7 D 4.96 4.89 4.81 28 D 5.525.24 5.18

Similarly, concretes can be made with an activator already having theretarder pre-incorporated into the activator solution. These havedemonstrated similarly enhanced plastic properties. This in someinstances provides a convenience for production of concretes at remotelocations without pre-blending all the components. Examples ofactivators made in this way can be found in Table 4.

TABLE 4 Activator Compositions Including a Retarder Percent Component 12 3 4 5 Boric acid 18.0 18.0 25.0 Potassium lactate 95.0 89.1 82.0 75.0Potassium hydroxide 32.8 Lactic acid 49.2

Table 5 shows the volume stability of concretes made with the lactateactivated cement. Their concrete design proportions are those shown inTable 3.

TABLE 5 ASTM C156 Shrinkage Values for Concretes in Table 1a Sample # 12 3 4 5 7 8 1 day −0.001 −0.006 −0.003 −0.003 −0.003 −0.006 −0.006 2 day−0.009 −0.010 −0.011 −0.009 −0.009 3 day −0.016 −0.012 −0.005 −0.007−0.011 7 day −0.020 −0.018 −0.014 −0.015 −0.021 −0.021 −0.020 14 day−0.024 −0.022 −0.019 −0.024 −0.028 −0.025 −0.025 28 day −0.029 −0.028−0.024 −0.029 −0.030 −0.027 −0.029Manufacturing Methods

The large area products (such as Example 4 in Table 2) may be producedby mixing all the ingredients except for the activator prior to use. Theactivator may then be added at the time when you need the concrete toinitiate its reaction. Once the activator is added, the chemicalreaction leading to final set has been started. The specific blend willdetermine how much working time is available prior to the final set.

For example, a transit truck may load a mix according to Example 4 at abatch plant. The transit truck now has 4-6 hours or more before theconcrete will no longer be useable. At any point in that time period,the activator, as a liquid or as a solid power, may be added (mostlikely at the construction site), and the concrete may be placed. Thisability provides a huge advantage over Portland cement concrete, whichtypically has 90 minutes of acceptable working time from the moment thetransit truck is loaded at the batch plant. Examples of concreteproduced in this way are show in table 6.

TABLE 6 General Use Concrete (Lactate based activator) Strength Curvesfor Different Binders Final Set Compressive strength Mix ID Data Min 24H 3 D 7 D 28 D 8142 ekkomaxx concrete Pot Lactate  7 H:30 M 336 16702222 3102 3.119%, Boric acid 0.9028%, Binder 500 lbs/cy, W/C 0.400 8143ekkomaxx Concrete with Pot Lactate  7 H:45 M 435 2113 3020 3797 3.119%,Boric acid 0.9028%, Binder 550 lbs/cy, W/C 0.349 8144 ekkomaxx concretewith Pot Lactate  8 H 665 2790 3829 5080 3.119%, Boric acid 0.9028%,Binder 600 lbs/cy, W/C 0.3155 8149 ekkomaxx concrete with Pot Lactate 10H:30 M 958 4386 5000 6105 3.119% Boric acid 0.9028%, Binder 650 lbs/cy,W/C 0.2645 8150 ekkomaxx concrete with Pot Lactate 10 H:45 M 1339 49115877 6911 3.119%, Boric acid 0.9028%, Binder 700 lbs/cy, W/C 0.2464 8151ekkomaxx concrete with Pot Lactate 11 H 1415 5032 6205 7439 3.119%,Boric acid 0.9028%, Binder 750 lbs/cy, W/C 0.2227 8157 ekkomaxx concretewith Pot Lactate 10 H:15 M 2308 5707 6990 7776 3.119%, Boric acid0.9028%, Binder 800 lbs/cy, W/C 0.2096 8158 ekkomaxx concrete with PotLactate 10 H 2453 5832 7066 8059 3.119%, Boric acid 0.9028%, Binder 850lbs/cy, W/C 8159 ekkomaxx concrete with Pot Lactate 10 H 2692 6213 72598391 3.119%, Boric acid 0.9028%, Binder 900 lbs/cy, W/C 0.192

The volumetric mixable products (for example, Examples 5 and 7 in Table2) may be made by adding uniform portions of cement, stone, and sandunder remote control operation. The cement portion containing both theaccelerator and the retarder may be blended with sand and stone in thehigh shear mixer. As an option to this approach, the accelerant andretarder may be added in either powder or liquid form.

This application discloses several numerical ranges in the text andfigures. The numerical ranges disclosed inherently support any range orvalue within the disclosed numerical ranges even though a precise rangelimitation is not stated verbatim in the specification because thisinvention can be practiced throughout the disclosed numerical ranges.

The above description is presented to enable a person skilled in the artto make and use the invention, and is provided in the context of aparticular application and its requirements. Various modifications tothe preferred embodiments will be readily apparent to those skilled inthe art, and the generic principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the invention. Thus, this invention is not intended to belimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein. Finally,the entire disclosure of the patents and publications referred in thisapplication are hereby incorporated herein by reference.

What is claimed is:
 1. A cementitious composition comprising: coal flyash-based pozzolans; a chemical activator based on lactic acid; and achemical retarder, wherein the cementitious composition is substantiallyfree of Portland cement, and the chemical activator based on lactic acidcomprises more than 50% by weight of the total weight of activators inthe cementitious composition.
 2. The cementitious composition of claim1, wherein the chemical activator is a pH neutral salt of lactic acid.3. The cementitious composition of claim 2, wherein the chemicalactivator comprises potassium lactate, sodium lactate, lithium lactate,calcium lactate, or magnesium lactate.
 4. The cementitious compositionof claim 2, wherein the pH neutral salt comprises an alkaline metal oralkaline earth.
 5. The cementitious composition of claim 1, wherein theretarder comprises a boron compound.
 6. The cementitious composition ofclaim 5, wherein the boron compound is selected from the groupconsisting of boric acid, boric oxide, sodium borate, sodiumtetraborate, potassium borate and potassium tetraborate, boraxpentahydrate, and borax decahydrate.
 7. The cementitious composition ofclaim 1, wherein cementitious composition is substantially free ofcitric acid activators, alkali metal activators, and metal carbonateactivators.
 8. The cementitious composition of claim 1, wherein thechemical activator based on lactic acid comprises more than 95% byweight of the total weight of activators in the cementitiouscomposition.
 9. The cementitious composition of claim 1, wherein thecementitious composition has a set time of between 2 hours and 24 hours.10. The cementitious composition of claim 1, coal fly ash basedpozzolans are selected from the group consisting of Class C fly-ash,Class F fly-ash, Class N pozzolanic ash and combinations thereof. 11.The cementitious composition of claim 9, wherein the composition has asilica to calcia molar ratio of between about 1.2:1 and about 1.4:1. 12.The cementitious composition of claim 1, wherein the retarder isdissolved in a solution of activator in a concentration between 0.1% and30.0%.
 13. The cementitious composition of claim 1, wherein the retarderis dissolved in a solution of activator in a concentration between 10.0%and 30.0%.
 14. A method of forming a hardened cement compositioncomprising: mixing a hydratable composition comprising coal flyash-based pozzolans, a chemical activator based on lactic acid to form ahardened cement composition and a chemical retarder, wherein the cementcomposition is substantially free of Portland cement, and the chemicalactivator based on lactic acid comprises more than 50% by weight of thetotal weight of activators used to form the hardened cement composition.15. The method of claim 14, wherein the chemical activator is a pHneutral salt of lactic acid.
 16. The method of claim 14, wherein thechemical activator comprises potassium lactate, sodium lactate, lithiumlactate, calcium lactate, or magnesium lactate.
 17. The method of claim15, wherein the pH neutral salt comprises an alkaline metal or alkalineearth.
 18. The method of claim 14, wherein the retarder comprises aboron compound.
 19. The method of claim 18, wherein the boron compoundis selected from the group consisting of boric acid, boric oxide, sodiumborate, sodium tetraborate, potassium borate and potassium tetraborate,borax pentahydrate, and borax decahydrate.
 20. The method of claim 14,wherein citric acid activators, alkali metal activators, and metalcarbonate activators are not mixed with the hydratable compositioncomprising coal fly ash-based pozzolans to form the hardened cementcomposition.
 21. The method of claim 14, wherein the chemical activatorbased on lactic acid comprises more than 95% by weight of the totalweight of activators used to form the hardened cement composition. 22.The method of claim 14, wherein the hydratable composition comprisingcoal fly ash-based pozzolans has a set time of greater than 2 hoursafter mixing with the chemical activator based on lactic acid.
 23. Themethod of claim 14, wherein the hydratable composition comprising coalfly ash-based pozzolans comprises pozzolans selected from the groupconsisting of Class C fly-ash, Class F fly-ash, Class N pozzolanic ashand combinations thereof.
 24. The method of claim 14, further comprisingdissolving a retarder in a solution comprising the chemical activator ina concentration of between 0.1% and 40%.
 25. The method of claim 14,further comprising dissolving a retarder in a solution separate from thechemical activator in a concentration of between 0.1% and 40%.